The Intergovernmental Panel on Climate Change’s major report on the science of climate change, published on 2 February 2007, predicts that temperatures will rise by 2°C and 4.5°C by 2100, relative to pre-industrial temperatures.
Below are estimates of the impacts for each degree of temperature rise. They are based on a major report published by Nicholas Stern, chief British government economist, in October 2006.
1°C rise
- Small Andean glaciers disappear, threatening water supplies for 50 million people
- Cereal yields in temperate regions increase slightly
- At least 30,000 people die every year from climate-related diseases, but winter mortality in Northern Europe and US drops
- 80% of coral reefs are bleached, including the Great Barrier Reef
- The Atlantic thermohaline circulation starts to weaken
2°C rise
- Water availability in some vulnerable regions (Southern Africa and Mediterranean) could drop by 20% – 30%
- Crop yields in Africa drop by 5% – 10%
- 40 – 60 million more people are exposed to malaria in Africa
- Up to 10 million more people are affected by coastal flooding
- Arctic species, including the polar bear and caribou, run a high risk of extinction
- The Greenland ice sheet could begin an irreversible melt
3°C rise
- In southern Europe, serious drought happens occurs every 10 years
- 1 to 4 billion more people suffer water shortages; up to 5 billion gain water but they could suffer increased floods
- Another 150 to 500 million people are at risk of hunger (if carbon fertilisation is weak)
- 1 to 3 million more people die from malnutrition
- The risk of abrupt changes in monsoons climbs
- There is a higher risk that the West Antarctic ice sheet, and the Atlantic thermohaline circulation, will collapse
4°C rise
- Water availability in Southern Africa and Mediterranean could drop by 30% – 50%
- African agricultural yields drop by 15% – 35%
- Up to 80 million more Africans are exposed to malaria
- Another 7 to 300 million people are affected by coastal flooding
5°C rise
- Some of the large Himalayan glaciers may disappear, affecting one quarter of the Chinese population and millions in India
- Ocean acidity continues to rise; marine ecosystems are seriously disrupted
- Sea level rise threatens small islands, low-lying coastal areas such as Florida, (Florida) and major world cities such as New York, London, and Tokyo
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